c# 异步编程demo (async await)

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Web;
using System.Threading;
using System.Threading.Tasks;

namespace TestApp
{
class Program
{
static void Main(string[] args)
{
Task<string> task = Call();
Console.WriteLine("测试");
Console.WriteLine(task.Result);

}
static string Greeting(string name)
{
Thread.Sleep(3000);
return string.Format("Hello, {0}", name);

}
static Task<string> GreetingAsync(string name)
{
return Task.Run<string>(() => { return Greeting(name); });
}
private async static Task<string> Call()
{

string result = await GreetingAsync("world");
return result;
}

}
}